Here’s what you should know about the flu, the flu shot and more from experts in the field.
What exactly is flu?
According to the CDC, the flu is “a contagious respiratory illness caused by influenza viruses.”
Influenza viruses directly infect the nose, throat and lungs. It can cause mild to severe illness and can even be fatal.
How does the influenza virus start?
Influenza actually originates among birds and other animals in Southeast Asia and then spreads to Europe and, lastly, the U.S., William Schaffner, chair of Vanderbilt Medical School’s department of preventative medicine, told ABC News.
How does the virus spread among humans?
Humans spread the virus we have in our throats to others when we touch each other, especially noses and mouths, Schaffner said.
Why are we so susceptible to the virus?
It’s because the virus comes in different forms, and several forms, every year, according to Schaffner.
Flu viruses are most common during the fall and winter, though seasonal flu viruses can be found year-round in the U.S.
According to the CDC, virus activity often increases in October and peaks between December and February. It can last through May.
What are the symptoms of flu?
Someone who is exposed to the flu virus may begin to experience the following symptoms about one to four days after exposure.
From the CDC:
Fever or feeling feverish/chills -- Note that not everyone will experience a fever.
Runny or stuffy nose
Muscle or body aches
Some may experience vomiting and diarrhea, though this is more common in children than adults.
How long is someone contagious after contracting the flu?
An infected person may be able to infect other people and spread the illness one day before they even begin to experience symptoms.
According to the CDC, the period of contagiousness can continue between 5-7 days after becoming ill.
The period of contagiousness could last even longer for those with weakened immune systems, especially young children.
Who is most at risk of getting the flu?
According to the World Health Organization, pregnant women, older people, young children and people with certain chronic health conditions -- such as asthma, diabetes and heart disease -- are most at risk.
What does the flu vaccine do?
The seasonal vaccine protects against the form of the virus scientists are predicting will be most comon during the upcoming flu season.
According to CDC experts, the traditional three-component flu vaccine protects against three flu viruses: H1N1, H3N2 -- both influenza A viruses -- and an influenza B virus.
The quadrivalent flu vaccine protects against those three plus an additional influenza B virus.